The present invention relates to the generation of electric fields to control movement of charged particles, and more particularly, but not exclusively, relates to the design and construction of devices to provide customized electric fields for charged particle analyzers.
When evaluating the composition of a substance, it is often desirable to study the behavior of charged particles taken from a sample of the substance of interest. Typically, the charged particles are liberated from the sample in the form of atomic or molecular ions--although in some instances it may be desirable to study subatomic particles bearing a charge. Various types of analyzers have been developed to facilitate the evaluation of charged particles, including ion mobility detectors, time of flight mass spectrometers, multipole mass spectrometers, and cyclotrons to name a few. U.S. Pat. No. 5,510,613 to Reilly et al., U.S. Pat. No. 5,504,326 to Reilly et al., U.S. Pat. No. 5,302,827 to Foley, U.S. Pat. No. 5,280,175 to Karl, U.S. Pat. No. 5,162,649 to Burke, U.S. Pat. No. 5,148,021 to Okanoto et al., U.S. Pat. No. 5,117,107 to Guilhaus et al., and U.S. Pat. No. 5,109,157 to Leon provide representative examples of various types of instruments directed to charged particle evaluation.
The application of charged particle analysis to the evaluation of biomolecules is one area in which there is increasing interest. Of particular interest is the mass sequence analysis of peptides, proteins, DNA fragments, sugars, and glycoproteins. Indeed, it is hoped that the spectroscopic evaluation of ions from biomolecules will provide more capable and cost-effective medical diagnostic equipment.
Central to the operation of most charged particle analyzers is the controlled generation of one or more electric fields (E-fields). Typically, analyzers utilize electric fields to accelerate, separate, and otherwise selectively direct charged particles. Expanded application of charged particle analysis often entails the careful design of an electric field tailored with various predetermined characteristics. Electric field gradient and spatial orientation of the electric field relative to the desired pathway of charged particles within the analyzer are examples of such characteristics.
For mass spectrum analyzers, the generation of a desired electric field frequently results in a complicated arrangement of numerous, expensively machined metal parts (sometimes called "lenses"). Typically, these lenses are spaced apart from each other along a tube, electrically interconnected, and then coupled to a voltage source to provide the desired electric field. The accurate orientation of these parts relative to each other and to the tube is often essential to generation of an electric field with the desired properties. Unfortunately, accurate assembly is very tedious and time consuming, and frequently presents a significant obstacle to obtaining the ideal electric field. Even if an acceptable electric field is finally obtained through careful adjustment of the various parts, the assembly is routinely torn down for cleaning as it becomes contaminated with the samples that pass through the tube. Disassembly, cleaning, and reassembly result in significant equipment downtime. In addition, this repeated assembly and disassembly subjects the parts to greater wear and tear.
In order to more readily advance charged particle analyzers to new applications, the ability to more rapidly and cost-effectively change electric field characteristics is in demand. The complex assembly and disassembly process associated with conventional charged particle analyzer lenses significantly impede such advancements. Furthermore, the multipiece arrangement of metal lenses limit the available electric field gradient and generally make analyzers larger--with a correspondingly higher power consumption--than would otherwise be desired.
Thus, there is a need for a simpler, more cost-effective technique to generate electric fields for charged particle analyzers. Preferably, this technique should reduce analyzer downtime and provide for the rapid interchange of components necessary to change electric field characteristics. The present invention satisfies these needs and provides other significant advantages.